HAha how about the mermaid princess in the recent episodes? Sanji would be jealous... but she does cry too much.

I'm gonna go with neither Nami or Robin or Boa and say that Luffy is too free a spirit to be tied up in a relationship, not to mention that he seems fairly uninterested. He just has adventure on his mind.

The thing with One Piece was that I never had any ships since I could never really see anyone getting together or having Oda write out a plot like that. Everyone in the group are very close nakama and it's nearly impossible to see it any other way especially in an adventure packed series like this one.

The way I see it is: the story is better off without serious romantic relationships. Any mainstream ships will be too awkward.